Ignition system



Aug 2, 1966 R. B. cLARK 3,264,486

IGNITION SYSTEM Filed D60. 4, 1965 Hic-Mp0 5 CM/QK BY E fe/ United States Patent C 3,264,486 IGNHTHN SYSTEM Richard B. Clark, Sidney, NX., assigner to The Bendix Corporation, Sidney, NX., a corporation of Delaware Filed Dec. 4, 1%3, Ser. No. 327,980 16 Claims. (Cl. 307-48) This invention relates to a magneto ignition circuit system and more particularly to certain improvements in iagneto ignition circuit systems of the type utilizing a saturable reactor means for limiting the level of the ignition discharge voltages applied to the igniter gaps of the system at the higher operational speeds of the magneto rotor.

This invention is a continuation-impart of the application, Serial No. 136,609, filed September 7, 1961 (now abandoned).

This invention is related to the application of Henry B. Gersoni, Serial No. 136,599, led September '7, 1961, for Magneto Ignition Circuit. As explained in the Gersoni application, in certain conventional ignition systems the magneto output winding is shunted by `a circuit breaker device which is periodically opened at a predetermined optimum fiux changing position of the magneto rotor thereby causing a voltage to be induced in the output winding. The magneto winding in these conventional systems is coupled via a suitable distributor and stepaup voltage means to the igniter gaps causing a discharge voltage of appropriate level to appear across and breakdown the particular gaps to which it is coupled at the time the circuit breaker is open. As is well known to those skilled in the art, the output level of the magneto is proportional to the speed of the rotor and, consequently, at the higher speeds the discharge voltage levels are far in excess of that required to re the igniter gaps thereby causing the detrimental effects stated in the aforesaid Gersoni application such as accelerated deterioration of the circuit breaker contacts, for example. These effects are substantially mitigated and/ or eliminate-d by the Gersoni invention, as explained in his aforementioned application, by providing a saturable reactor having -a square loop hysteresis characteristic that is coupled in a parallel coupling relationship with the output winding of the magneto. Thus, at higher operational speeds of the magneto rotor, the saturable reactor is readily saturated by the corresponding relatively higher output level voltages of the magneto and as a result the impe-dance of the inductor is lowered so yas to short circuit effectively some of the energy output of the magneto winding thereby limiting or reducing the available discharge voltage applied to the particular igniter gaps to which it is connected at the time. However, at the lower operation magneto rotor speeds and consequently lower level voltage outputs, the saturable inductor is adapted to remain in an unsaturated condition and hence the output of the magneto is applied substantially undiminished to the igniter gap to be tired. It is to be understood, that the level provided by the magneto output must be large enough to lire the igniter gap within the predetermined contemplated operational speed range of the magneto rotor. For further explanation and details of the foregoing, the reader is referred to the aforesaid Gersoni application.

The present invention comprises a magneto ignition circuit system, similar to that described by the Gersoni application, which further provides utilization means for utilizing the output generated by the magneto in excess of that required by the ignition system. Thus, the magneto, voltage step-up means, discharge gaps, and discharge voltage-limiting means in the system disclosed herein are essenti-ally the same as those disclosed in the aforementioned Gersoni application. In the particular illustrative embodiment of the present invention there is combined in 3,254,186 Patented August 2, 1966 ice the magneto ignition circuit system, means to utilize the current generated by the magneto in excess of the ignition requirements to charge a battery. The battery in turn is utilized for boosting or supplementing the magneto in the starting and low speed ranges thereof.

The invention has among its objects the provision of a novel magneto ignition circuit of the type wherein the discharge voltage is limited in the higher speed range of the magneto, such system including utilization means for utilizing the output developed by the magneto in excess of that required for ignition purposes.

l Another object of the invention resides in the provision, 1n a system of the type above indicated, of means for charging a battery by such excess current.

A further object of the invention lies in the provision, in a system of the type indicated immediately above, of a novel circuit arrangement whereby the battery may be selectively used for boosting or supplementing the output of the magneto and thereby reduce the lower limit of the operational speed range of the system.

The above and further objects and novel features of the invention will more fully appear from the following `description when the same is read in connection with the accompanying drawing. It is to be expressly understood, however, that the drawing is for the purpose of illustration only, and is not intended as la denition of the limits of the invention.

In the drawing, wherein like reference characters refer to like parts,

The single gure of the drawing is a schematic diagram of a preferred embodiment of the magneto ignition circuit system of the invention.

Referring now to the sole figure, there is illustrated a magneto 10 comprising output winding 11, core 12, and the magnetic field producing element or rotor 13. Coupled in parallel with the output winding 11 is an arcreducing condenser 14. Circuit breaker 15, having stationary contact 15a and movable contact 15b associated therewith, is also adapted to be coupled in parallel with the output winding 11 when the switching means, indicated generally by the reference numeral 16, is in a predetermined appropriate position as explained more fully hereinafter.

ln the particular embodiment chosen to illustrate the principles of the invention, the magneto ignition system is shown as a four gap ignition system which comprises a compatible distributor 17 having four angularly spaced electrodes 18 and a center electrode 19 of the rotatable `distributor finger 2t). Each electrode 18 is adapted to be coupled to suitable voltage step-up means illustrated as a voltage step-up transformer comprising primary and secondary windings 21a an-d 2lb, respectively, which -are grounded at their common junction 21e as shown in the flgure. Each of the secondary windings 21h is shunted across an igniter gap 22, the latter being shown as grounded `at 22a. For the sake of clarity, the respective step-up transformers and igniter gaps, which are associated with the two electrodes 18 located on the left side of the distributor 17 as viewed in the figure, are not shown and are indicated in block form as blocks 23 coupled thereto, the elements of blocks 23, it being understood being identical to the elements shown contained in the respective blocks 23', illustrated in broken outlines, which are coupled to the electrodes 18 located on the right side of the distributor 17. The center electrode 19 is coupled to the switch contact 24a of switch 24, the arm 24b of which is coupled to the upper end of the magneto winding 11. Thus, with the arm 24b of switch 24 in engagement with the contact 24a, each primary winding 21a will be pla-ced in parallel coupling relationship with the magneto winding 11 when the respective electrode 18 is in contact with the linger 20.

As an alternative, each of the igniter gaps may, if desired, be associated with a common step-up voltage means by suitable modification of the circuit. Thus, for example, the upper end of winding 11 could be coupled, by positioning the -arm 24b of switch 24 to engage the contact 24C, to the upper end of the primary winding 25a of the common step-up transformer 25. The other end of the primary winding 25a of transformer 25 `is grounded at the junction 25e and coupled to the lower end of secondary winding 25h. The upper end of the secondary winding 2517 of transformer 25 is coupled to the center electrode 26 of the rotatable distributor linger 27 of distributor 28 which is illustrated in the g-ure as being of the type having a gap between the electrodes 29 and finger 27. Each of the electrodes 29 of distributor 2S is coupled to an igniter gap 30, which is illustrated as being grounded. For the sake of simplicity, the igniter gaps coupled to the electrodes 29 located on the left side of distributor 28 are not shown in detail but are illustrated in block 4form as blocks 31. It is to be again understood, that the elements contained in blocks 3.1 are identical to the elements shown in the blocks 31', the latter being illustrated in broken outlines. In this manner, the igniter gaps of blocks 31, 31 are commonly coupled via distributor 28 to a single step-up transformer 25.

Also adapted to be coupled in a parallel coupling relationship with the output of winding 11, when the switching means 16 is in an appropriate position hereinafter specified, is a saturable reactor 32 which limits the level of the ignition discharge voltages applied to the igniter gaps of the system at the higher operational speed in `a manner as substantially disclosed in the aforesaid Gersoni application.

A utilization means, indicated generally by reference numeral 33, is provided for utilizing the output developed by the magneto which is in excess of that required for ignition pur-poses. The utilization means may comprise, for example, a circuit for powering a light and/ or powering an indicator and/or powering a radio and/ or charging a battery. In the preferred embodiment illust-rated in the drawing, the utilization means 33 comprises a circuit for charging Ia battery 34 with the magneto output in a manner hereinafter described. The -last mentioned circuit comprises rectifier means, illustrated, by way of example only, as two half wave rectiiiers 36 and 37 in the form of a pair of parallel inversely connected diodes, the battery 34 being serially connected in the branch containing diode 36. The parallel connected branches are connected via resistor 38 to the saturable inductor 32. By appropriate positioning of the switch means 16, as `hereinafter explained, the battery 34 is adapted to be charged by the magneto output. In addition, the battery 34 is adapted to be coupled to the magneto winding 11 and thereby raise the level of the magneto voltage at the lower operating speeds of the rotor 13 by appropriate positioning of the switching means 16 as hereinafter explained.

As is well known to those skilled in the art, the magneto rotor 13 is geared to the engine shaft, not shown, of the engine utilizing the ignition system and is coupled via the shaft indicated by the dash line 39 to the cam 40 which operates the circuit breaker 15. The magneto rotor 13 and cam 40 -are so positioned with respect to each other on the shaft 39 so that when the normally closed contacts of breaker `15 are opened, a maximum rate of flux change is induced in the winding 11. The rotating dist-ributor nger or 27, which is likewise 4adapted to be geared to the shaft 39 by suitable gearing means, not Shown for sake of clarity, is adapted to be in contact or proximity, respectively, with one of its respective electrodes 18 or 29 when the contacts of breaker 15 open and the rate of change of flux in winding 11 is at `a maximum.

Switching means 16 are illustrtaed by way of example as comprising three mechanically interconnected switches 41, 42, 43, each having three switching positions I, II,

4 III corresponding to their respective stationary contacts 41a, 41b, 41C, etc. The respective arms 41d, 42d, 43d are mounted on a common shaft indicated by the dash-dot line dd. The arms 41d, 42d, i3d are so positioned on the shaft 44 so that they `are in simultaneous engagement with their respective appropriate contacts.

As shown in the figure, arms 41d, 42d, and 43d are connected to the cam operated contact I15b of breaker 15, the grounded side of winding 11 of magneto 10, 4and the saturable inductor 32, respectively. Each of the contacts 41a, 4211, 42e, 43a and 43C `are disconnected or open contacts. Contacts 41b and 41C are connected to the grounded side of winding 11 and the positive terminal of battery 34, respectively. Contacts 42a and 43h are connected to the upper side of winding 11.

When the switching means 16 is in the position designated I, the circuit breaker 15, `battery 34 and saturable inductor are disconnected from the winding 1.1 and the system is in the off condition which is preferably chosen to correspond to the off condition for the engine utilizing the ignition system of the figure. If desired, a bleed-off resistor, not shown, may be serially connected between the conductor 45 and contact 42a to discharge the condenser 14 should there be any residual charge remaining thereon cause-d, for example, by suddenly returning the system to the off position before the `charge on condenser 14 can be dissipated. This last mentioned resistor, not shown, would also prevent damage to the winding 11, which would 'be otherwise short-circuited in the off position, should the engine shaft or rotor 13 be accidentally rotated, for example, by external means While the ignition system is in the off position.

In the switching position designated II, the system is in the on or running condition and corresponds to the on condition for the engine. In this position II, the circuit breaker 15 is connected across the output of winding 11, and the saturable inductor 32, via the series connected resistor 33 `and utilization means or circuit 33 is also connected across the output of winding 11. Thus, in that position II the rotor 13 is driven by the engine shaft, not shown, causing an output voltage proportional to the speed of rotor to appear at the output of winding 11. An A.C. voltage output is short-circuited by and dissipated in the contact breaker system luntil the time when the breaker contacts 15a and 15b are opened temporarily by the coaction of cam 40 and rotor 13 and the rate of ux change induced in winding 11 is at a maximum, as -aforedescribed If the speed of the rotor 13 is relatively low then the inductor 32 does not saturate an-d remains an effective high impedance across the coil 11. As `a result, the output of coil 11 is applied directly, depending on the relative position of switch 24, to either the contact 19 of distributor 17 or the upper end of the primary winding 25a, and in either case `if the speed of the rotor is sufficient to provide an output voltage having a level llarge enough to cause firing of the particular gap connected at the time thereto, then ignition will occur thereat when the breaker contacts open. If, on the other hand, the speed of the rotor 113 is relatively high then the inductor 32 is rapidly saturated causing some of the excess of the output power of the winding 11 to be short circuited and thereby limits the level of the voltage and hence power output of winding 11 applied to the contact 19 or winding 25a, as the case may be, the level being sufficient however to cause the particular gap to be fired. This excess power is utilized by utilization means 33 `and in the preferred embodiment is utilized to charge the battery 34. Diode 36 is poled to pass the positive half cycles of the excess A.C. voltage and current to the battery 34 and block the negative half cycles thereto. Diode 37 permits the negative half cycles to by-pass the battery 34.

In the third position of the switching means 16, designated III, the battery 34 is serially connected to the circuit breaker 15 and this series combination is shunted across the output of winding 11 and inductor 32 is disconnected from the circuit. The third position III is preferably chosen to correspond substantially to the relatively lower operational speed condition of the rotor 13 which in the absence of the battery 34 would produce an output voltage in the winding 11 insuihcient to cause firing of the particular gap t-o which it was connected at the same -time the breaker contacts a, 15b are opened. Thus, in this position III, w-hen the contacts 15a, 15b are closed a D.C. current from `battery 34 is superimposed on the A.C. current in the winding 11, the A.C. current being induced Aby the rotating member 13. When the breaker contacts 15a, 15b open, an output voltage from winding 11 having a level suicient t-o cause firing of the particular ga-p to which it is coupled is thus provided.

The saturable reactor 32 in the illustrative embodiment takes the form of a coil having a saturable core with substantially square loop hysteresis characteristics. The core of such coil may, for example, be made of material which is sold commercially under the name Toroid Delta-Max. In a typical such coil, employed in a circuit similar to that shown in the figure but with an S-Cylinder magneto having an output of 14 kv. at 300 r.p.rn., a satisfactory coil has 180 turns of #21 wire wound on a Delta-Max core IT5233. The condenser 14 may have, for example, a capacity of .74 mfd., and the resistor 38 may have a resistance of 178 ohms, with a current carrying capacity of 1 watt.

The ignition circuit in accordance with the invention displays advantages not only by reason of its use of a discharge voltage limiting reactor 'but by reason of its conservation of the excess current generated -by the magneto which otherwise would be wasted. The system makes possible the provision or" a self-contained ignition system which includes its own booster Ibattery and automatically maintains the battery in charged condition.

Although only one embodiment of the invention has been illustrated in the accompanying drawing and described in the foregoing specification, it is to be expressly understood that various changes, such as in the relative dimensions of the parts, materials used, and the like, as well as the suggested manner of use of the apparatus of the invention, may be made therein without departing from the spirit and scope of the invention as will now be apparent to those skilled in the art. Thus, although a half-wave rectifier system has been shown in the battery-charging circuit, it will be understood that, if desired, an appropriate full wave rectifier may be employed in order to utilize both sides of the wave of alternating current which passes from -the saturable reactor to the battery-charging circuit. Further, as above indicated, the excess current generated by the magneto instead of, or in addition to, charging a battery may be used for a variety of other purposes such as, for example, powering a light, an indicator or a radio.

What is claimed is:

1. An ignition circuit comprising a magneto having a winding, breaker contacts connected across the winding, at least one set of electrodes constituting a discharge gap connected to the winding to be energized thereby, and a saturable reactor and a load connected in series across the winding in parallel with the breaker contacts and with the connection between said winding and said discharge gap.

Z. An ignition circuit accor-ding to claim 1, wherein the reactor has a saturable core and a winding magnetically coupled to the core.

3. An ignition circuit comprising a magneto having a winding, breaker contacts connected across the winding, at least one set of electrodes constituting a discharge gap connected to the winding to be energized thereby, and a circuit having a saturable reactor and a load in series therewith adapte-d to be connected across the winding in parallel with the breaker contacts, the said circuit including a rectifier for delivering rectified current to the load.

4. An ignition circuit according to claim 3, wherein the load comprises a battery to be charged through the rectifier.

5. An ignition circuit according to claim 1, wherein the magneto is `of the low tension type, and comprising a voltage step-up transformer interposed in the lconnection between the winding of the magneto and the discharge gap.

6. An ignition Icircuit according to claim 5, wherein the reatcor has a saturable core and a winding magnetically coupled to the core.

7. An ignition circuit according to claim 6, comprising a plurality of sets of electrodes constituting discharge gaps, wherein there is a voltage step-up transformer in series with each discharge gap, and comprising a distributor interposed between the winding of the magneto and the step-up transformers.

8. An ignition circuit according to claim 6, comprising a plurality of sets of electrodes constituting discharge gaps, wherein there is a common voltage step-up transformer connected to said magneto winding for said discharge gaps, and comprising a distributor interposed between said voltage step-up transformer and said plurality of sets of electrodes.

9. An ignition circuit comprising a magneto having a winding, breaker contacts connected across the winding, at least one set of electrodes constituting a discharge gap connected to the winding to be energized thereby, a circuit having therein a saturable reactor, a rectifier, and a battery connected in series, means selectively to connect said circuit across the winding in parallel with the breaker contacts and to disconnect it therefrom, and further means selectively to connect the battery to the winding of `the magneto so as to increase the current flow therein.

10. An ignition circuit yaccording to claim 9, wherein the first named means and the further means are alternatively operable.

11. An ignition circuit comprising at least one discharge gap, a magneto having rotor means and winding means to provide an output voltage proportional to the speed of said rotor means, circuit breaker means connected across said winding means and adapted to be open for at least one predetermined angular position of such rotor means, means to connect said discharge gap to said winding means whenever said rotor means is in said predetermined position, saturable reactor means connected to said winding means in a parallel relationship and adapted to be saturate-d whenever the level of said output voltage is in predetermined excess of that required to discharge said gap, and utilization means connected to said saturable reactor means to utilize the saturation current thereof.

12. An ignition circuit according to claim 11, wherein the saturable reactor means comprises a saturable core and a winding magnetically coupled thereto, said core having a substantially square loop hysteresis characteristic.

13. An ignition circuit according to claim 11, wherein said utilization means comprises a battery and circuit means for charging said battery.

14. An ignition circuit Iaccording to claim 13, wherein said circuit means comprises a rectifier interposed between said saturable reactor means and said battery for delivering a rectified current to said battery.

15. An ignition circuit according to claim 13, comprising selective switching means having at least one position for connecting said battery of said utilization means to said circuit breaker means to supplement the discharge potential applied to said gap and another position for connecting said utilization means and said saturable yreactor across said winding means.

16. An ignition circuit according to claim 15, wherein the first mentioned switching position of said switching means is effectuated at speeds of said rotor means which are insucient, per se, to cause a voltage to be applied to said gap to discharge thereacross.

References Cited by the Examiner UNITED STATES PATENTS Hooven 315-214 X Brinson 123-148 Tognola 315-217 Cook 315-172 ORIS L. RADER, Primary Examiner.

LLOYD MCCOLLUM, Examiner.

T. J. MADDEN, Assislant Examiner. 

1. AN IGNITION CIRCUIT COMPRISING A MAGNETO HAVING A WINDING, BREAKER CONTACTS CONNECTED ACROSS THE WINDING, AT LEAST ONE SET OF ELECTRODES CONSTITUTING A DISCHARGE GAP CONNECTED TO THE WINDING TO BE ENERGIZED THEREBY, AND A SATURABLE REACTOR AND A LOAD CONNECTED IN SERIES ACROSS THE WINDING IN PARALLEL WITH THE BREAKER CONTACTS AND WITH THE CONNECTION BETWEEN SAID WINDING AND SAID DISCHARGE GAP. 